This invention relates to a closed container used in a semiconductor manufacturing system, in a clean room, for manufacturing semiconductor wafers, liquid crystal display boards, reticles, disks, etc.
One example of a semiconductor manufacturing system of this type is as shown in FIG. 3. In FIG. 3, reference numeral 1 designates a surface treatment equipment incorporating a surface treatment oven or furnace for providing surface treatment to semiconductor wafers, the equipment 1 having two ports (described later) arranged in parallel; 2, a wafer inspecting device; 3, a self-running type positioning robot; 4, a wafer storehouse; 4A, the apron of the wafer storehouse 4; 5, a wafer washing device; and 6, a linear motor conveyor.
FIG. 4 is a sectional view showing a part of the aforementioned surface treatment equipment 1. In FIG. 4, reference numeral 10 designates a closed container with an opening 11 which is sealingly closed through a seal 12 with a lid 13. The lid incorporates an automatic locking mechanism (not shown) with a rod 14. The rod 14 is moved back and forth, so that its end is engaged with the opening 11 of the container 10. Further in FIG. 4, reference numeral 15 designates a wafer cassette, in which a plurality of semiconductor wafers W (for instance twenty-five semiconductor wafers W) are set one above another. The wafer cassette 15 is set in the container 10 when conveyed. FIG. 4 shows the container 10 including the wafer cassette 15 which container is placed on a plate 16 of the surface treatment device 1. The plate 16 forms the abovedescribed port (or cassette taking-in-and-out port) 16A. The container 10 is locked onto the plate 16 with lever-type locking mechanisms 17, and thereupon the self-locking mechanism of the lid 13 is released. The wafer cassette 15 together with the lid 13 is placed on the stand 18 of a lift 18 and moved downwardly, and then only the wafer cassette 15 is conveyed to the surface treatment oven (not shown) by the conveyor (not shown). After the surface treatment of the semiconductor wafers has been accomplished, the wafer cassette 15 is moved back to the lid 13 set on the lift stand 18A. Thereafter, the lift stand 18A is moved upwardly, so that the wafer cassette 15 is brought into the container 10. Under this condition, the lid 13 is locked; that is, the container 10 is closed with the lid 13 thus locked. The container 10 thus closed is moved into the wafer storehouse 4 through the apron 4A by the robot 3. In the wafer storehouse 4, a stacking crane 7 is operated to set the container 10 at a predetermined position on a shelf specified by a central control device (not shown).
Semiconductor wafers or the like should be free from dust. Therefore, a semiconductor manufacturing process is carried out in a clean room having a clean atmosphere, and heretofore the wafer cassette 15 is not covered when conveyed from one processing device to another. However, as the integration of semiconductor circuits is improved, the wafer cassette 15 is handled as follows: That is, the wafer cassette 15 is set in the closed container 10 before moved between processing devices. In addition, the closed container 10 is filled with inert gas, to suppress the formation of natural oxide films on the semiconductor wafers.
The container is held closed. However, if it is left for a long time after being filled with an inert gas such as N.sub.2 gas, the gas leaks gradually, so that the density of N.sub.2 gas in the container is decreased.
Therefore, in the case where it is required for the container to have a high purity N.sub.2 gas atmosphere, or the container is held in the storehouse for a long time, it is necessary to supplement the container with more gas. For this purpose, the container is conveyed to the N.sub.2 gas purge station every predetermined period of time, and gas-purged. This makes the system intricate in operation.